(Technical Field)
The present disclosure relates to an ignition device of an engine. More particularly, the present disclosure relates to an ignition device of an engine controlling streamer discharge and arc discharge.
(Description of the Related Art)
An ignition device of an engine supplies a primary current to a primary coil electrically connected to a power source so as to store magnetic energy in an ignition coil. Then, a secondary current is induced when the primary current is cutoff. Allowing the secondary current to flow between a gap formed between a center electrode and a ground electrode of an ignition plug, spark discharge occurs at the gap. As another type of ignition device, a configuration is provided in which high frequency current is made to flow through the above-mentioned spark discharge path via a diode, thereby producing spark discharge having a high energy and discharge plasma in wider area than the normal discharge.
In such ignition devices, since a large amount of current is required so as to increase an area of the discharge plasma, there has been a problem that the electrode is consumed significantly faster. To solve this problem, JP-A-2014-211148 discloses a technique, that is, discharge is cutoff before the temperature of the electrode reaches a melting temperature of the metal, and current is allowed to flow again, and this process is repeatedly performed, thereby minimizing consumption of the electrode.
According to the technique disclosed by the above-mentioned patent literature, electrode consumption is suppressed by repeating the above-described process several times. However, in a view of the electrode consumption, this technique still has to be improved.